Chevrolet Q&A

When driving at 65mph or above, speedo needle will jump around ( jumps from 65 mph to 40 mph ) then returns to normal. This action takes place in a matter of 1 to 2 seconds. The SES light will flicker when this happens but no codes will be stored.
This will happen about once or twice every minute to minute and a half.
My main concern's are will it mess up the ECU? and how do I fix it?